Drilling Fiberglass??

I agree 100% with PAR, if you can clamp the jig (board) tightly in place it helps.

Cut the square holes a little small, but just a little, and try to angle the cut out, so you remove more of the core than the surface. This way you can block (use a block of wood, the lagrest possible) sand the flat sides and they will stay straight and even. If you have to sand away the core at the same time, it will be much harder to do.

 

We use the jig saw blades that are coated with an abrasive (no teeth!) and now use them exclusively.

They can get quite hot and seem to suffer no damage , working in solid layup up to 1/2 inch thick.

Holes in any composite will need to be sealed . Preferably by removing a bit (1/4 to 1/2 inch of core and filling with epoxy and filler.

FF

 

I'll have to find some of those abrasive blades, Fred....
The suggestion of cutting the core back a bit within the hole and filling with thickened epoxy is a good one. It has the added advantage of strengthening the rim of the hole against the forces applied to the rim by whatever object or fastener goes through it. Sandwich composites are great with distributed loads but don't like point loading very much.

 

the blades are called carbide tipped,, or carbide coated,, they make rough cuts tho,, and most time going slow doesnt help on the chipping,, and the thinner the glass is,, the more damage they do., i usually try taking a dremil to it first,,using one of them grinding stone bits,, outline what your cutting,, but to the inside of ya line,, you can either cut with carbide blades after or use any of the other techniques mentioned to finish cutting and taking the core out

 

The grit edge blades can be found at most good hardware stores and they make different grits, you can get fine, medium and course. Most places don't carry all three though. Edge chipping has a great deal to do with technique, pushing hard and cutting fast on a thin poorly stabilized panel will cause chipping, doing the just the opposite will normally give much better results.

 

These work great.

http://www.forestcitytool.biz/

 

At my old job we used carbide tipped hole saws. Only they had a single carbide tooth vs. your traditional blade that has 50 or more teeth. Its no doubt the cleanest hole you can get in fiberglass.

Heres what they look like:
http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO=4480533&PMT4NO=0

And you guys already mentioned flush trim router bits, and carbide grit jig saw blades. Totally agree with you guys on that one.

 

Personaly, I would drill a series of holes with a high speed hand drill and then just connect the dots. This allows for a couple of things; first, you don't have to worry about chipping, and you can "score" a line with a compass between the holes. To finish the circle, a porter cable router with a plywood template--1/4 inch nice and flexable for the radius--will work nicely

 

I use carbide tipped hole saws, with a 6mm pilot drill centre for holes. When about half way through, go inside and drill out again from there. The end result is a perfectly cut hole.

If this hole is below waterline, such as a skin fitting, I then get a bent nail, put it into a drill, and smash out the core materila with it inside the hole. This can then be easily sealed again with clear epoxy, followed by bogged epoxy (talk and epoxy) to fill the hole back again. Run the hole saw gently through the hole when dried, and the end result is just like a bought one.

The skin fitting can then be inserted and tensioned without any compression showing on the skin.

Hope this helps.

 

Oh, yeah, drill slowly, as if it is metal. as stated above by someone else.

 

Brisbane....is that Australia?

 

Yep.

Hi ratrace2, i just responded to your laminate schedule on another thread.

 

heres a few photos of my system to trim i use a diamond straight router bit and a die grinder at 25,000 rpm, i tooled a collar to fit on the end of the grinder, the jigs are steel cut on the waterjet table a plywood jig would work good for a one off, all i do is plung the bit into the glass a inch away from the cut line and run along the jig perfect cuts with out any gel chipping away, the outside of the part i use the part it self as a jig

 

Rather than marking the blank fiberglass panel, make up an entire panel pattern in 3/4" plywood including all holes arranged exactly like the finished layout . Surface mount holes for wires can be drilled first in order to bolt the ply pattern onto the helm.
Once bolted on, hole saws won't wander and the surroundinf surfaces won't be exposed. LOW speed works best on the bigger holes. A normal sheet metal hole saw will work fine. Speed creates heat, which softens the cutting teeth, hence the slow speed, and an assistant can spray water into the action to help cool the hole saw (make sure the tool's grounded through a GFIC, wear gloves, etc.
I cannot over-emphasize the slow drilling speed with the larger size hole saws. If your plywood pattern is perfectly made (use a drill press), your finished helm will be identically perfect.

Alan

 

One caution is to only use air tools before the grinding to bond surface is done.

Air tools will spray a bit of their required lube oil , so bonds may be suspect without extra grinding.

GG